This invention generally relates to a one-way spring clutch assembly, and more specifically to such an assembly having bearing means for carrying a thrust load. The invention also relates to an application of the clutch assembly in preventing reverse rotation of a shaft such as a ball screw under a thrust load as applied through a ball nut.
Spring clutches are well known in the art as exemplified in U.S. Pats. Nos. 2,784,810, 3,410,379, 3,637,056, 3,797,618, and 4,246,991, the entirety of which are incorporated herein by reference. It is known in the art to apply a spring clutch in combination with a ball screw and nut assembly as exemplified in U.S. Pat. No. 4,246,991, and it is further known to apply a spring clutch with bearing means for carrying thrust loads, such as through a ball nut and screw, together with a friction plate for resisting reverse rotation of the shaft under thrust load.
One such known spring clutch assembly has first and second clutch members where one of the clutch members has a flange for securing it to a housing so that it does not rotate, and where neither clutch member is secured to the shaft for rotation therewith. Instead, the other clutch member engages a friction plate located between the clutch member and a disc secured to the shaft. The present invention represents an improvement over these prior art spring clutch assemblies.
Generally, the spring clutch assembly of the present invention comprises first and second clutch members mounted on a shaft such as a ball screw for rotation about a common axis. The shaft is mounted for rotation relative to a housing. Between the clutch members are thrust load bearing means which may be ball bearings seated in annular races in facing surfaces of the clutch members. A torsion spring surrounds the clutch members, such that torsion loads rotating the shaft in one direction tend to unwind and loosen the torsion spring allowing one clutch member to rotate relative to the other, and torsion loads tending to rotate the shaft in the opposite direction tend to wind and tighten the torsion spring against the outer surfaces of the clutch members to lock the clutch members against rotation of one relative to the other. Neither clutch member is secured to the housing so that no flange is needed and a narrow profile can be maintained.
In a particular application of the spring clutch assembly in accordance with the invention, means such as a friction plate are provided between one of the clutch members and the housing preventing reverse rotation of the shaft as would be caused by a thrust load.
In a preferred embodiment of the invention one of the clutch members is secured to the shaft for rotation therewith. This is accomplished by the clutch members having a mating hub and recess with the hub having a transverse open slot for receiving a locking pin which extends through the shaft to lock the clutch members to the shaft. By this construction, the clutch member may be molded of powdered metal which is comparatively inexpensive.
These and other objects and advantages of the invention are apparent from the drawing and detailed description to follow.